Voltage Drop Introduction and Solutions

Views: 0 Author: Anny Publish Time: 2021-08-09 Origin: https://www.suntechleds.com/

Constant voltage(CV) and constant current(CC)

CV: When the various parameters in the constant voltage circuit are determined, the output voltage is fixed, but the output current changes with the increase or decrease of the load.

CC: The output current of the constant current drive circuit is constant, and the output DC voltage changes within a certain range due to the difference in load resistance. The smaller the load resistance, the lower the output voltage, and the larger the load resistance, the higher the output voltage.

What does voltage drop mean

Most LED light strips use a constant voltage circuit. Standard 12V because it can be used in one section due to the segmented operability of the light strip, in addition to the constant voltage of 12V or 24V, which is usually 12V or 24V for ease of control (such as RGB dimming). It becomes the power supply. All samples are in constant voltage source + current limiting resistor + LED mode. However, with this type of circuit connection, if the connection length is too long, voltage drop problems will occur.

voltage drop

Voltage drop refers to the voltage that each part of the entire circuit drops from the 100% voltage of the initial power supply. Excessive voltage drop will make your LED light burn dimly. The voltage drop indicates how the energy supplied by the voltage source decreases as the current flows through the passive components of the circuit (components that don't provide voltage).

What cause voltage drop

In the DC circuit, the voltage gradually drops along with the light of the LED strip. In this way, for every foot of wire, along the length of the wire, the available voltage per foot decreases steadily. This may cause one end of the light bar to be brighter than the other. One of the root causes of the voltage drop is the realization of the wrong connection type and the additional distance between the LED strip light and its power supply.

The voltage drop is that the power supply distance of the light strip is too long, the terminal voltage will decrease, and the brightness will also decrease. Generally speaking, the closer the light strip is to the plug, the brighter it is, and the farther it is, the darker it is. When using a low voltage light strip, if one end of the light strip is connected to a transformer (12v / 24v), the farther the other end of the light strip is, the voltage drop will occur. Simply put, the end close to the transformer is brighter, and the end far away from the transformer becomes darker. Different color LEDs will have different voltage drops.

voltage drop of colors

Yellow-green (565-575nm), Yellow (585-595nm), Red (600-650nm): The voltage drop of LED is 1.63-2.18v (average 2.0v); Working current 20ma = (5.0-2.0)v/150Ω. The voltage drop of Blue (465-475nm), Green (500-535nm) and White LEDs is 2.38-4.0v (average 3.3v); working current 20ma = (5.0-3.3)v/85. If you do not pay attention to the LED wavelength, only the forward voltage drop of the LED, the maximum forward working current (usually 50mA), and the minimum light-emitting forward current. Considering the life of the LED, the working life is long if the forward current is small, generally 5-10mA, and the brightness is enough. There is also a reverse breakdown voltage. The forward voltage drop of the LED is different for different light (wavelength).

Maximum working current: 30mA/25℃: visible light with normal brightness; 50-300mA/℃: visible light LED with high brightness.

LEDs are different from ordinary diodes in that their turn-on voltage is relatively high. The working voltage of 3.3V mentioned here is its voltage drop at 20MA working current (average value, each individual will have a difference). After the white LED is turned on, the tube voltage drop gradually increases with the increase of the working current. The working current of the LED should be strictly controlled when using it. The power of the LED is not large, if it exceeds the rated working voltage or working current, it will burn out quickly.

The influence of voltage drop on LED strips

LED strip voltage drop

1.Cable thickness

For long-distance cables, you will need to use thick cables to prevent voltage drops; for short-distance cables, you can use thin cables without worrying about voltage drops. The thickness of the cable is the most important factor affecting the voltage drop: if the cable used is very thin, it will cause the long distance of the cable to decrease.

2. Cable material

Just like electric current, the material of the cable also affects its ability to conduct electric current. Some materials have more resistance than others.

3. The length of the LED strip

The voltage drop will not only appear on the cables used to power the LED tape, but also on the LED tape itself. As a general rule, any LED tape that runs continuously for more than 5 meters will start to experience voltage drop issues.

How to solve voltage drop problem

Divide the long LED strip into shorter strips, then connect the excess "parallel" wire from the power supply to each new LED strip. You can repeat this process the same number of times as needed. It is also possible to line up the excess wires from the power supply unit with the uncut LED strips and connect them when the voltage drops begin to occur. Just make sure to use the correct wire gauge, as described below.

Example 1: Create a parallel connection from the power supply and split the operation in all directions. If 60-foot LED tape is to be used for lighting, we recommend installing a power supply during operation and extending a 30-foot section from the power supply side and a 30-foot section to the other side.

parallel connection

Example 2: Run different parallel LED strips over longer distances: If you want to install a continuous line of more than 90 feet, or if you want to use a longer wire from the power supply to the power strip, use a "parallel" connection. Please see the picture below:

pareller connection